This Week's Sky at a Glance, October 13 – 22

By: Alan MacRobert October 13, 2023 0

FRIDAY, OCTOBER 13

■ Vega is the brightest star very high toward the west these evenings. Less high in the southwest is Altair, not quite as bright. Just upper right of Altair, by a finger-width at arm's length, is little orange Tarazed. Down from Tarazed runs the stick-figure backbone of the constellation Aquila, the Eagle, along the Milky Way.

SATURDAY, OCTOBER 14

■ Annular eclipse of the Sun today. The path of annularity crosses Oregon, northern Nevada, Utah, New Mexico, west-central and south Texas, Central America, Colombia, and Brazil.

Annular eclipse May 10, 1994 — *S&T*'s Rick Feinberg snapped this image of the annular solar eclipse that some of us watched crossing the United States on May 10, 1994.

A partial solar eclipse will occur over a much wider area: practically all of North, Central, and South America and the Caribbean.

Maps. Timetable for cities and towns in the path of annularity. Timetable for the partial eclipse elsewhere in the US. Timetable for Canada. More about this eclipse is in the October Sky & Telescope starting on page 34, and plan your eclipse-sequence photography starting on page 60.

Online are Fred Espenak's Observing October's Annular Eclipse and Jay Anderson with how to chase clear skies as the hours count down: When It's Eclipse Decision Time, How Do You Decide Where to Go?

Cloudy? Or are you away from the zone of action? See Where to Watch the Annular Eclipse Online.

■ New Moon — because, of course, it's solar eclipse day! The exact time of new Moon is given in almanacs as 1:55 p.m. EDT. This time refers, as always, to a hypothetical observer at the center of the Earth.

SUNDAY, OCTOBER 15

■ Now that it's mid-October, Deneb has replaced Vega as the zenith star after nightfall (for skywatchers at mid-northern latitudes). Accordingly, Capricornus has replaced Sagittarius as the zodiacal constellation low in the south.

MONDAY, OCTOBER 16

■ The Great Square of Pegasus is now high in the east-southeast after dark, still, for now, more or less balanced on one corner in early evening (for the world's mid-northern latitudes).

TUESDAY, OCTOBER 17

■ Look for bright Capella sparkling low in the northeast these evenings. Look for the Pleiades cluster about three fists at arm's length to its right. These harbingers of the cold months rise higher as evening grows late. Watch for Aldebaran to come up below the Pleiades.

Upper right of Capella, and upper left of the Pleiades, the stars of Perseus lie astride the Milky Way.

WEDNESDAY, OCTOBER 18

■ This is the time of year when soon after nightfall, W-shaped Cassiopeia stands on end (its fainter end) halfway up the northeastern sky — and when, off to its left in the north, the dim Little Dipper extends left from Polaris.

THURSDAY, OCTOBER 19

■ By late evening the Great Square of Pegasus is getting very high in the southeast — and it's tilting clockwise off of one corner to lie more level like a square. Autumn is advancing.

The Great Square's right-hand edge points far down toward Fomalhaut, by about four fists at arm's length. Its left edge points less far down, and less directly, to Beta Ceti (Diphda or Deneb Kaitos). Fomalhaut is 1st magnitude, Beta Ceti is 2nd mag.

■ Double shadow transit on Jupiter. Late tonight in the early morning hours of Friday the 20th, two of Jupiter's moons will cast their shadows onto Jupiter's face at once. For details and timetable see Bob King's Orionid Meteors Fly; Two Moons Shadow Jupiter.

FRIDAY, OCTOBER 20

■ The Moon, a day short of first quarter, shines low in the south right at the end of twilight. Before the Moon gets any lower, use binoculars to see that it's sitting almost smack on the four-star handle of the Sagittarius Teapot.

SATURDAY, OCTOBER 21

■ First-quarter Moon (exact at 11:29 p.m. EDT). The Moon is now in the dim area between Sagittarius and Capricornus, almost smack on top of Herman's Cross, a.k.a. The Dogs: the little four-star asterism described and mapped in the September Sky & Telescope, page 43. Its stars are all about magnitude 4½ , quite a bit fainter than those of the Teapot's handle. Definitely use binoculars. Herman's Cross is 2° from end to end.

■ The Orionid meteor shower should be near its peak tonight. The good Orionid-watching hours are from about 1 a.m. to the first light of dawn Sunday morning. The Moon will have set. This shower is a modest one; in a very dark sky you might see 8 or 10 meteors per hour. The shower's radiant is in the east at Orion's dim club, between Betelgeuse and the feet of Gemini.

SUNDAY, OCTOBER 22

■ This is the time of year when the Big Dipper lies down horizontal low in the north-northwest after dark. How low? The farther south you are, the lower. Seen from 40° north (New York, Denver) even its bottom stars twinkle nearly ten degrees high. But at Miami (26° N) the entire Dipper skims along out of sight just below the northern horizon.

This Week's Planet Roundup

Mercury is out of sight in conjunction with the Sun.

Venus, brilliant at magnitude –4.6 in Leo, shines high in the east before and during dawn. It rises nearly 2½ hours before dawn's first light — a weird witching-hour apparition on the eastern horizon.

Look before the sky brightens and you'll spot Regulus, only 1 percent as bright, above Venus. They're separating now. Regulus is 5° over Venus on the morning of the 14th, widening by nearly 1° per day to 11° from Venus on the 21st.

And can you spot Gamma Leonis (Algieba), a little fainter, 8° left or upper left of Regulus? It's a fine binary star for telescopes: magnitudes 2.4 and 3.6, separation 4.7 arcseconds.

In a telescope Venus now shows itself at dichotomy: half lit.

Mars is out of sight behind the glare of the Sun.

Jupiter (magnitude –2.8, in Aries) rises in the east-northeast in twilight. It dominates the east later in the evening and shines highest in the south after midnight. It's on its way to opposition November 2nd.

Jupiter with Io resolved while half eclipsed, Oct. 5, 2023 — Jupiter and Io imaged by S&T's Sean Walker on the morning of October 5th, while Io was entering eclipse by Jupiter's shadow. South is up. This image is so high-resolution that Io's disk is clearly resolved as half-lit!
Walker used his observatory-mounted 14-inch Schmidt Cassegrain scope. This is one of a series of five images he assembled from video frames spanning the three minutes that Io took to enter Jupiter's shadow. "I had to limit the video to only 20 seconds [per image] so the shadow line didn't make stacking too weird. It took hours to process these."

Saturn (magnitude +0.6, in dim Aquarius) is the brightest "star" in the southeast in twilight. It's highest in the south around 10 p.m. Fomalhaut twinkles two fists at arm's length below it.

Saturn (and Dione) Aug 30, 2023 — Saturn on August 30th, imaged by Christopher Go. South is up. Saturn was barely past opposition then, so the globe's shadow on the rings behind it was barely becoming visible on the east side (at the right here). The shadow on the rings now is wider and more prominent.

Uranus, magnitude 5.6 in Aries, is 10° east of Jupiter.

Neptune, magnitude 7.8 at the Aquarius-Pisces border, is nice and high 25° east of Saturn.

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions and graphics that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time minus 4 hours. UT is also known as UTC, GMT, or Z time.

Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For a more detailed constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.

Once you get a telescope, to put it to good use you'll need a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows all stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo edition — The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown here is the Jumbo Edition, which is in hard covers and enlarged for easier reading outdoors by red flashlight. Sample charts. More about the current editions.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to mag 9.75). And be sure to read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning the sky. And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

But finding a faint telescopic object the old-fashioned way with charts isn't simple either. Learn the tricks at How to Use a Star Chart with a Telescope.

Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye heavens above. It's free.

"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996

"Facts are stubborn things."
— John Adams, 1770